onProcessed.js

Quagga.onProcessed(function (result) {
  var drawingCtx = Quagga.canvas.ctx.overlay,
    drawingCanvas = Quagga.canvas.dom.overlay;

  if (result) {
    if (result.boxes) {
      drawingCtx.clearRect(0, 0, parseInt(drawingCanvas.getAttribute("width")), parseInt(drawingCanvas.getAttribute("height")));
      result.boxes.filter(function (box) {
        return box !== result.box;
      }).forEach(function (box) {
        Quagga.ImageDebug.drawPath(box, { x: 0, y: 1 }, drawingCtx, { color: "green", lineWidth: 2 });
      });
    }

    if (result.box) {
      Quagga.ImageDebug.drawPath(result.box, { x: 0, y: 1 }, drawingCtx, { color: "#00F", lineWidth: 2 });
    }

    if (result.codeResult && result.codeResult.code) {
      Quagga.ImageDebug.drawPath(result.line, { x: 'x', y: 'y' }, drawingCtx, { color: 'red', lineWidth: 3 });
    }
  }
});